International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) 14496-10 (Moving Picture Experts Group (MPEG)-4 Part 10 Advanced Video Coding) or H.264, which is video compression/encoding technology jointly standardized in ISO/IEC and International Telecommunication Union-Telecommunication Standardization (ITU-T), an ISO/IEC 14496-10 Amendment 3 (MPEG-4 Scalable Video Coding) standard, a video codec-1 (VC-1), which is an Society of Motion Picture and Television Engineers (SMPTE) standard, an audio video coding standard (AVS), and the like have achieved significant advance in terms of video data compression efficiency.
There are various factors for improving video compression efficiency. In particular, a process of sub-dividing a macroblock in units of 16×16, 16×8, 8×16, 8×8, 8×4, 4×8, and 4×4, prediction-encoding sub-blocks, and encoding a block for minimizing cost in an optimum block mode in terms of rate-distortion cost is performed, unlike existing video encoding standards (MPEG-1 Video, MPEG-2 Video, MPEG-4 Part 2 Visual, H.261, H.263, and the like) in which prediction encoding is performed after a size of a picture to be encoded is divided in units of macroblocks (each of which has 16×16 pixels).
Thereby, a micro motion or a motion of a complex video may be more effectively predicted, and compression efficiency may be significantly improved by significantly reducing a generated residual signal.
FIG. 1 is a diagram showing seven types of motion prediction block divisions used in H.264 as division block types of 16×16 macroblock unit blocks to be encoded in an H.264/advanced video coding (AVC) encoder of the related art.
In a block-based prediction encoding method as shown in FIG. 1, an encoding process is generally performed by dividing an input video into macroblock units having a size of 16×16. In particular, in the ISO/IEC 14496-10 (MPEG-4 Advanced Video Coding) or H.264 standard, prediction encoding is performed by dividing a macroblock into seven types of sub-blocks as shown in FIG. 1 and finally selecting a block for minimizing the rate-distortion cost.
When intra encoding of sub-blocks into which a 16×16 macroblock to be encoded is divided is performed, the macroblock is subjected to intra prediction encoding in a size of one 16×16 pixel unit. Alternatively, after the macroblock is divided into sub-blocks, intra prediction encoding of four 8×8 blocks or sixteen 4×4 blocks is performed.
In general, the above-described intra prediction encoding technique efficient in terms of the reduction of the number of cases of various block modes in low definition video encoding, but has a problem in high definition (HD) or ultra high definition (UHD) video encoding. That is, in the case of a super-macroblock having a size of 32×32 or more to which a 16×16 macroblock as an encoding unit block is extended, encoding efficiency is degraded if all divided block modes within the super-macroblock are applied to the same intra prediction based on a 16×16, 8×8, or 4×4 block as in the existing method.
In other words, it should be noted that all divided blocks are encoded by only intra or inter prediction encoding in a prediction encoding method based on division blocks in the related art. That is, only one of the intra prediction encoding and the inter prediction encoding is selected and applied to a division block without applying both the intra prediction encoding and the inter prediction encoding to the division block. This may result in a gain of encoding efficiency in image or video compression at an HD rate or less due to simplicity of a syntax expressing a block encoding mode obtained by applying only one of intra and inter encoding, but may become a factor that degrades the encoding efficiency when a unit of encoding is a super-macroblock that has the same or greater size than a macroblock.